IET 525 System Analysis and Simulation

1. IET 525 System Analysis and Simulation • Instructor: William J. Bender, Ph.D., PE, • Office phone: 963-3543, Home # 509 933-3583 E-mail: benderw@cwu.edu please call or write • Web Page www.cwu.edu/~benderw/benderw.html this page has syllabi, exams, and handouts • Teaching Philosophy this is a graduate course students do a lot of reading and learning on our own. Class is for reviewing concepts, discussion, and group exercises. Labs are performed on students time “doesn’t have to be Wed night” • Syllabi

2. IntroductionChapt 1 • Need for Modeling & Simulation • Terminology • Model Building • Simulation • Simulation Modeling & Analysis McGraw-Hill, by Law & Kelton • Discrete -Event Simulation Prentice Hall, by Banks, Carson, & Nelson • Simulation of a Bank Teller • Data Collection/ Statistics • Apply what you know pg 17

3. Needfor Modeling & Simulation • Chemicals, Pharmaceuticals, hospitals, shipping, retail, defense, electronics, construction, manufacturing, shipping, communications • …all industries need a method to “try something out” before building or changing a process/ manufacturing line. • Bottom line helps decision makers solve complex problems by providing a systematic process to develop data, experiment and see what happens

4. Simulation • “Building logical & mathematical models of real or proposed systems & use PCs to experiment with the parameters/ resources of the system. • We will simulate systems via a simulation language called Visual SLAM…very user friendly • AweSim is a program that runs the simulation & animates Visual SLAM … very user friendly • one of many…I learned Extend a graphical simulation package that my dissertation was formed around

5. Rules Weather Construction System Trades, Equip, Material, Processes, etc Suppliers Design System • We will perform “Systems Analysis” by modeling and simulation systems & see what happens • A system is “Interdependent items that describe the area of interest or perform a specific function” • And is defined by the SCOPE of the problem we are trying to solve

6. Rules Weather Construction System Trades, Equip, Material, Processes, etc Suppliers Design System • External forces may effect system • Include • Ignored • Treated as inputs

7. Models • Models are the description of systems/ abstract of the system • Physical ie WSU hydraulic lab • Math ie Differential equations, logical (CPM) • Graphical ie visual computer displays • First models are built…then simulated to understand interactions of elements

8. Boundaries Simulate & Solve Problem System Model Goal Performance Model Building • Key is defining the elements of the model/ system & how they interact with each other • Problem statement or Goal • Established boundaries • Performance measures/ Design alternatives • Takes an iterative process

9. Parameters Solve Problem Model Simulate Design Performance Simulation • Build Models and experiment with it on a computer • Benefits • Work out bugs before built if proposed ie hospital/ man line • W/O disturbing operating systems • NTD

10. Simulation StatesDiscrete or Continuous • Continuous = constantly changing ie weather, waves, auto pilot • Discrete Event = Small incremental steps ie construction, bank teller, manufacture line, etc • Deterministic ie 10 minutes or 2 days • Stochastic ie normally distributed, mean =10, std =2

11. Simulation of Bank Teller • An example to show where we are going… • Want to model the operations of a bank determine how long a person waits in line and % of time a teller is idle • Model is: Served by teller Customer Arrives Exit bank Wait for teller % of time idle? How Long?

12. Simulation of Bank TellerConcepts • At any instant model is in a particular state • As events occur, state changes • Events define the model Served by teller Customer Arrives Exit bank Wait for teller % of time idle? How Long?

13. Simulation of Bank Teller Pg 8& 9

14. # in line Time Simulation of Bank TellerEvent oriented Description To track customers in line & teller busy or idle at discrete points in time Pg 10 & 11

15. Simulation of Bank TellerEvent oriented Description • Need Data • At any point in time the model is in a particular state • Need “Book keeping” function to track changes • Two perspectives 1)Customer 2)Teller Busy Teller Status Idle Time

16. Data Collection & Analysis • Use existing Data or Collect Data • Existing data, ie census, cost data, government…may be easily obtained but typically very broad • Surveys especially for qualitative material..Delphi • Field Studies/ experimenting, expensive but best type • Descriptive Statistics

17. Data Collection & AnalysisDescriptive Statistics • Grouping Data • Group Data into cells for Frequency Distribution or Cumulative Frequency • Displayed graphically as Histogram # of People Ave wait time

18. Data Collection & AnalysisDescriptive Statistics • Parameter Estimation • Population = All possible observation • Sample = only part of population • Can estimate Population with mean =  and variance = 2 • From a sample can find mean & variance to describe a population

19. Data Collection & AnalysisDescriptive Statistics • Distribution Estimation • Use a know statistical distribution to estimate a population, ie normal, beta, exponential, weibel

20. Chapt 1 Summary • Build Model based on goal, parameters, design, performance • Simulate to experiment with model and solve problem • Can use statistical estimation for data

21. Chapt 1 Exercises • # 1-2 pg 18 Build a model for the MSET program from the students point of view similar to Figure 1-1 • # 1-6 Describe/ draw the functional/mechanical operation of a car using boxes connected with arrows, use chassie, engine, transmission, wheels …by developing a model. How can this be simulated to understand the performance characteristics of Speed, MPG, cargo capacity, cost, performance ie 0-60mph time

22. Chapt 1 ExercisesSolution • # MSET program model similar to Figure 1-1 Rules/ degree requirements Financial MSET Course Interest Project interest Available Classes Advisor/ Committee Others?

23. Chapt 1 ExercisesSolution • # 1-6 Describe/ draw the functional/mechanical operation of a car using boxes connected by arrows, use chassie, engine, transmission, wheels …by developing a model. How can this be simulated to understand the performance characteristics of Speed, MPG, cargo capacity, cost, performance ie 0-60mph time Chassie engine Trany Wheels Simulate by changing:weight, wheel base, engine size, engine turbo, engine gas/ diesel, trany gears, wheel size and out put performance of speed, MPH, HP, Size, Cost…others

24. Chapter 2 Simulation Modeling Perspectives • Modeling World Views • Discrete Simulations • Continuous Simulations • Visual SLAM

25. Simulation World Views • The functional relationship of how a system is perceived and described • Either: • Discrete • Dependent variables change at specific points in simulated time • Continuous • Dependent variables continuously change in simulated time

26. Discrete • Discrete = Dependent variables change at specific points in simulated time • Construction of a road, Dependent Variable = % complete, specific lane openings • Window assembly line, Dependent Variable = people idle/busy, machine idle/busy • Bank Teller Dependent Variable = # of customers, teller idle busy Dependent Variable Event Times

27. Continuous • Continuous = Dependent variables continuously change in simulated time • Sine wave approximation of an ocean wave Dependent variable is the height of the wave • Position of a space craft Dependent variable is exact location in orbit • Auto pilot of an aircraft, Dependent variables are speed, bearing, attitude, etc Dependent Variable Time

28. Combined • Both discrete and continuous • Some activity develops slowly over time and at a specific event the state changes • Chemical process, slowly reaches a certain concentration then a catalyst is added an an explosion occurs Dependent Variable Event Times

29. Discrete Simulation Modeling • Goal = Reproduce the activities the entities are engaged in to learn about the behavior of the system. • Entities = Objects within the boundaries of discrete system ie people, machines, $, resources • Activities = discrete function, unit of work • Event = Start or stop of an activity • Process = sequence of events that includes several activities

30. Discrete Simulation Modeling Discrete Sim formulated by 3 methods: • Event Orientation = Define changes in the state at each event time (Busy/Idle) • Activity Scanning Orientation = Describe the activities which entities engage in (system state based on activities condition) • Process Interaction orientation = Describe process which activities flow (CPM)

31. Discrete Simulation ModelingEvent Orientation • Define changes in the state at each event time (Busy/Idle) • Done by: Determine the events that can change the state of the system & use logic to model the system • ie Bank System • Status of teller • # of customers • Performed by maintaining a calendar of events and cause their execution simulated time

32. Discrete Simulation ModelingActivity Scanning Orientation • Describe the activities which entities engage in (system state based on activities condition). • Done by: describing activities & prescribe conditions which cause an activity to start or end • Not used much (must scan all activities) except when an activity is indefinite or determined by a prescribed condition

33. Discrete Simulation ModelingProcess Interaction Orientation • Describe process which activities flow (CPM) • Simulation that includes elements that occur in defined patterns • Manufacturing/ construction/ where you want to understand the entire process

34. Discrete Simulation ModelingProcess Interaction Orientation Model the flow of entities thru a system & define a sequence of events that are executed by the simulation

35. Continuous Simulation Modeling • Dependent Variables change continuously over time • Models are frequently written as derivatives….or differential equations • State variable S (wave height/ speed) over time T want to determine the response of the variable over time • Or integrate ds/dt over time using numerical integration methods using simulation

36. Visual SLAMAweSim • Visual SLAM is the computer language that is specifically written for simulation • AweSim is the software product that combines language with modern window, graphics…makes SLAM user friendly • Visual SLAM able to do discrete simulations as event or process orientations or both. Also does continuous and combined continuous/discrete.

37. Visual SLAMAweSim • Consists of nodes and branches to model queues, servers, machines and decision points. • DE modeler defines the events and the changes to the system when events occur • Continuous model is represented by diff eq that describe the dynamic behavior of of the state variables

38. Modeling Perspectives Summary • Discrete Simulations...three orientation mostly use • Event • Process • Continuous Simulations • Defined by diff eq for constant changes • Visual SLAM/ AweSim • Computer Language that performs simulation • Will become clearer when we work with a simulation

39. Modeling Perspectives Exercises • Page 32 • # 2-3 Paint shop describe system using event orientation and process orientation • #2-4 Describe HVAC control in terms of state variables, time events and state events

40. Modeling Perspectives Exercises Solutions • # 2-3 Paint shop • event orientation 4 events, 1) arrive to prep area, 2) complete prep, 3) arrive at spray machine, 4) end spray/take out • process orientation essentially visualize an entity going thru the following sequence waiting for prep, prep, travel to spray, wait for spray, spraying • #2-4 Describe HVAC control • state variable = temperature • time events = reset thermostat, turn on heat or cool, breakdown, lose power • state events temperature crosses the thermostatic setting….moisture content to turn on/off humidifier